A hydraulic excavator includes a bucket cylinder, an arm cylinder and a boom cylinder respectively for operating a bucket, an arm and a boom, the cylinders driven by a hydraulic circuit (see, for instance. Patent Document 1). The hydraulic circuit includes a hydraulic oil tank for storing hydraulic oil, a hydraulic oil pump for supplying the cylinders with the hydraulic oil from the hydraulic oil tank, the cylinders hydraulically driven by the hydraulic oil from the hydraulic oil pump and a control valve for switching the supply of the hydraulic oil to the cylinders. The hydraulic oil in the hydraulic oil tank is supplied to the cylinders via the hydraulic oil pump and the control valve to operate the cylinders.
Some hydraulic excavators, especially small-size hydraulic excavators employ an arrangement where the hydraulic oil tank, which is generally disposed next to an operator cabin, is disposed below a floor to enlarge a cab for improving its comfortability (see, for example, Patent Document 2).
[Patent Document 1] JP-A-200)-39117 (FIG. 1)
[Patent Document 2] JP-A-2003-278185 (FIG. 2)